Not Your Typical Electrical Gremlin MC8

[Melbo]

I'm sure there is a simple explanation and an easy fix but I can't figure it out.

I have a transplanted L10 in an MC8 and the alternator that is on the engine has it's own regulator.

There are two wires connected to the voltage regulator one shows approx 24 volts and one shows approx .4 volts.

The wire which shows 24 volts is connected to stud #5 in the remote start panel ( also connected is wire marked 57A ).  The wire which shows .4 volts is connected to stud #33 in the rear panel ( by the air filter ) and this wire has a tag on it marked R1.

The large wire (0000 welding cable) runs to the start batteries and everything works just fine.

NOW FOR THE QUESTION

With the old 8V71, voltage regulator and generator I had the cable from the generator run to an isolator and it fed the start batteries and the house batteries.

Now if I connect the cable from the generator on the L10 to the isolator the not gen light flashes and the cable from the alternator shows only 1.4 volts.

Reconnect the cable to the start batteries and everything works like it is supposed to.

I have come up with several work arounds that require an extra step or two to get the house batteries charged while I'm driving but I prefer the simplicity and transparency of the isolator ( I paid for it I wanna use it ).

If anyone has an idea of what to do I would appreciate it.

Thanks  Melbo

[boogiethecat]

Just a guess, some alternators need to be hooked directly to a battery to bootstrap themselves into working.  An isolator is basically a couple big diodes that keep voltage from going backwards, ie with an isolator in the circuit the alternator would not "know" that it's hooked up, as 12 volts from the battery wouldn't make it's way back to it.  It's possible I guess that this is keeping your alternator from working, being that some alternators need 12 volts on them to "get them excited".

If you hook up the isolator and start the engine, alternator not working, then momentarily short out the isolator, does the alternator only work when it's shorted out, or does it stay working thereafter? That'd be a clue...

Cheers
Gary

[Melbo]

Thank you for the suggestion

I could hook up the engine generator to the house batteries not the start batteries and see if it starts charging because they are independent but use the same ground ( the chassis ) and that would let me know if the 24 volt to start the charge is related to the bus system or separate. I also have a 24 volt solenoid that I could connect and see if the momentary connection starts the charging -- it will be interesting to see if it continues to charge when I open the solenoid.  I will try both of these later today and let you know.

Melbo

[JohnEd]

Melbo,

As a forward biased diode don't you loose .7 volts dropped across it?  For this device to "work well" I think you need to have the alt voltage sampled/controled by the physical bat terminal.  A loss of .7 volts will seriously cripple the charge rate of a bat.  You don't deserve that, no matter how much you paid.

What capacity alternator are you using?  I bought a 100 amp isolator years ago and I shudder to think what a 300 amp item would cost.

Good luck,

John

[boogiethecat]

John, These days if an isolator is made properly (if that's even possible!) it'll have schottky diodes in it instead of regular silicon diodes. Schottky diodes have more like .15 to .3 volt drop instead of .7   and I agree while this is better, it still screws your alternator's ability to deliver a full charge, and no matter 'who' argues 'what' here, (ie "I've had mine for years with no problem" kinda logic), isolators are NOT good for batteries, period.

Melbo, I'd actually recommend dumping the isolator and change over to a solenoid system which has zero diode drop and will keep your batteries in top condition.  My opinion: isolators are bad ideas at best, or for stick and staples at worst, and shouldn't even be considered in a bus with expensive batteries
Cheers
Gary

[Melbo]

Gary and John Thanks for the heads up

I don't remember batteries ever being cheap but I will still use the isolator. I got it from WRICO when I got my inverter.

Now for the report on what I found.

The charge worked with the house batteries  and when I reconnected the generator to the input and then momentarily crossed the input and output on the isolator the generator began charging and kept charging.

I didn't take note of the exact input and output but the input from the generator was 28 volts and change and the out put was 27 volts and change.

So as a solution I am going to install a momentary switch that will activate a solenoid to get the charge started and everything should operate as it used to.

Thanks again for all help once again proving that this board can solve problems more quickly than a person by themselves.

Melbo

[JohnEd]

Boogie El Gato,

Thank you for that info.  You always come thru for me.  Many thanks ad regards to the family in this holiday season.

John

[junkman42]

Melbo, I have an motorla alternator on a perkins diesel in a sailboat that I charge three battery banks with using an isolator.  I use a diode to feed voltage from one bank to the alternator which when connected to the sense terminal on the alternator will provide the correct charge to the batterys.  I do not know if You have this option on Your alternator but it may be food for thought.  When sensing the voltage at the batterys a islolator does not cause any problems and is a simple way.  My two cents, not worth much in the overall scheme of things!  John

[boogiethecat]

I have a tendency to be somewhat negative about things I don't like (me?  hee hee )
and isolators are one of them.  But there are always ways to make things work, and I decided to think about it a bit more.  Still, I'd never install one of my own...

So in defense of isolators, Yeah  something like John mentioned directly above will work perfectly...or if you have an adjustable alternator you could adjust it's output higher by the appropriate amount to compensate for the isolators' diode drop, and it would work equally as well. 

Cheers
G

[Melbo]

Well it's time to bring this GHOST up again.  I have to make a change to my set up or set up an automatic shipment of voltage regulators.

I replaced the regulator when my system quit charging and on the new regulator there was a setting to compensate for the isolator which I used.

Well on the last road trip on the way home from Mexico the new regulator stopped working.

My guess is that the regulator doesn't like my isolator (or the isolator can kick the regulators butt) or something like that.  I would prefer to fix this so I don't have to do it again. I am thinking about abandoning the isolator but was also wondering if I connected the house or start batteries (but not both) directly to the cable from the alternator at the center post of the isolator and then connected the other set of batteries to an outside post does it still keep the systems separate or am I beating a dead horse here.

Should I just get a solenoid (rated for 400 amps) and use that OR is it just a fluke that I have ruined two regulators.

Melbo

[JohnEd]

Well it's time to bring this GHOST up again.  I have to make a change to my set up or set up an automatic shipment of voltage regulators.

I replaced the regulator when my system quit charging and on the new regulator there was a setting to compensate for the isolator which I used.

Well on the last road trip on the way home from Mexico the new regulator stopped working.

My guess is that the regulator doesn't like my isolator (or the isolator can kick the regulators butt) or something like that.  I would prefer to fix this so I don't have to do it again. I am thinking about abandoning the isolator but was also wondering if I connected the house or start batteries (but not both) directly to the cable from the alternator at the center post of the isolator and then connected the other set of batteries to an outside post does it still keep the systems separate or am I beating a dead horse here.

Should I just get a solenoid (rated for 400 amps) and use that OR is it just a fluke that I have ruined two regulators.

Melbo

Can't believe The Cat didn't say somthing.  WEith me you get the second string.  I solators have solid state devices inside, I learned that from Boggie, and regulators of the modern variety also have solid stated devices inside.  These devices can talk to each other and wreck havoc.  An EE can theorize the c rap out of this and for 20K givew you a paper...whoppee!  I would keep the isolators in the circuit.  I would move the battery voltage pick-up for the alternator to the bat termnal and let the alt voltage rise to the level that charges the batteries....14.5V(?)  If you charge too much youe batteries won't last and too little and you will be running them into the grouind to get and service.  Also bad.

I am going with the solinoid that straps in the house batteries into parallel with the start bats WHILE the engine is running.  If you hear anything bad about doing it that way I would appreciate a heads up.  If you configure a switch into the affair you can switch in you house bats to augment/boost your start bat.  Nice feature that you miss with a isolator alone.

Good luck Melbo,

John

[Melbo]

Funny you should post this just now (funny interesting not laughable funny) --- Today I am going to finish up wiring a solenoid for the start batteries and 12 volt converter.  I am going to let the alternator at the engine run directly to the house batteries because I use them for the bulk of the electrical power (AC etc) from the engine. The way I read the diagram for the regulator the house batteries will call for a charge and I can use the solenoid to send power to the start batteries and converter as necessary.

Thanks for the response --- I hope this solves the problem.

Melbo

[JohnEd]

John, These days if an isolator is made properly (if that's even possible!) it'll have schottky diodes in it instead of regular silicon diodes.  isolators are NOT good for batteries, period.
Cheers
Gary

Gary, Well, no, I didn't know that and as was always the case in the past I have again learned something from you.  Thanks for that.

But "why" aren't isolators good for batteries?  I got rid of mine cause it was rated for only 60 amps.  I now have a system that can exceed that charge rate and isolators just burn out.  The .7 volt issue I had dealt with by having the alt sample at the battery....as you suggested long ago.

Cheers right back at'cha,

John